Anomalies in the overall shape of the eye can cause visual disorders. Hyperopia ("farsightedness") occurs when the front-to-back distance in the eyeball is too small. In such a case, parallel rays originating greater than 20 feet from the eye focus behind the retina. In contrast, when the front-to-back distance of eyeball is too large, myopia ("nearsightedness") occurs and the focus of parallel rays entering the eye occurs in front of the retina. Astigmatism is a condition which occurs when the parallel rays of light do not come to a single point within the eye, but rather have a variable focus due to the fact that the cornea is aspherical and refracts light in a different meridian at different distances. Some degree of astigmatism is normal, but where it is too high, it must often be corrected.
Hyperopia, myopia, and astigmatism are usually corrected by glasses or contact lenses. Surgical methods for the correction of such disorders are known. Such methods include radial keratotomy (see, e.g., U.S. Pat. Nos. 4,815,463 and 4,688,570) and laser corneal Ablation (see, e.g., U.S. Pat. No. 4,941,093).
Another method for correcting those disorders is through the implantation of polymeric rings in the eye's corneal stroma to change the curvature of the cornea. Previous work involving the implantation of polymethylmethacrylate (PMMA) rings, allograft corneal tissue, and hydrogels is well documented. One of the ring devices involves a ring design that allows a split ring to be inserted into a channel dissected in the stromal layer of the cornea using a minimally invasive incision through which the channel for the implant is created and through which the implant is inserted.
U.S. Pat. No. 4,452,235, to Reynolds, describes a method and apparatus for corneal curvature adjustment. The method involves inserting one end of a split end adjusting ring into the cornea of the eye and moving the ring in a circular path until its ends meet. The ends are thereafter adjusted relative to each other until the shape of the eye has assumed a desired curvature whereupon the ends are fixedly attached to maintain the desired curvature of the cornea.
Although the procedure for introducing ICRs into the intracorneal stroma is known, our inventive insertion devices used to implement these procedures is not shown.
Vacuum devices useful for ocular surgical procedures are, however, common. For instance, U.S. Pat. No. 4,423,728, to Lieberman, shows a cam-guided trephine for selectively cutting a circular or V-shaped groove about the cornea. The device utilizes a pair of suction rings which affix the apparatus onto the sclera of the patient's eye. The vacuum is usually less than about 10 cm of water thereby avoiding raising the intraocular pressure above the physiological levels. The suction ring lies in the anatomically constant area just outside the limbus.
Similarly, U.S. Pat. No. 4,997,437 to Grieshaber, shows a process and apparatus for cornea grinding. The device has a base member which is held to the conjunctiva of the eye by vacuum space formed about the periphea of the cornea. A rotary grinder is attached to the base member and slides onto the eye through the interior bore of the base member. No provision is made for preventing rotation of the base member.
None of these disclosures shows the combination of devices similar to those disclosed herein.
Suggestion of blunt points or dissectors for producing channels within the interlamellar boundaries are found. See, for instance, U.S. Pat. No. 5,090,955, to Simon and "Intrastromale Implantation Eines Justierbaren Kunstofforings Zur Hornhau Trefraktion Sanderung", Hartmann et al., Konare B der Deutschen Gesellschaft fur Intraok ularlinsen Implantation delivered by H. Freylev et al Springer-Verlag Wein, pp. 465-475. They do not suggest the special relationship shown with the dissector support.
An optional aspect of this invention is the use of pins which engage the front of the eye to prevent rotation of the inventive device during use.
U.S. Pat. No. 4,429,696, to Hanna, shows a surgical apparatus for precisely cutting out the cornea of the eye by making at least one circular incision. The device is held to the front of the eye by a series of claws, which optionally may be retractable, and suction placed on the central portion of the eye during the cutting operation. There is no suggestion of using the claws in cooperation with an annular vacuum ring.
Finally, the invention may optionally include a soft base conformable to the surface of the eye.
Such devices are known. See, for example, published PCT Application WO91/08711, to Kilmer et al., shows a device for re-profiling a cornea. The device rests on a resilient vacuum ring which is adapted to sit on the sclera portion of an eye which surrounds the cornea which is to be re-profiled. The top side of the vacuum ring has a number of positioning pins which allow it to be connected to the remainder of the profiling apparatus.